Interference by acetaldehyde is observed when the acetaldehyde concentration is higher than approximately 250 mg/L in the 0.05 mL sample using the TSO2 Manual Assay Procedure (see Table 1). At acetaldehyde concentrations higher than 250 mg/L the total sulphite reaction is slower than stated in the TSO2 Manual Assay Procedure but generates the expected absorbance change when the reaction is allowed to complete. At a concentration of 1250 mg/L acetaldehyde in the sample, the TSO2reaction takes ~ 15 minutes to complete (at 25°C).

 

TABLE 1. Acetaldehyde Interference in the TSO2 Manual Assay. Reactions were performed using the TSO2 Manual Assay Procedure in 1 cm path-length cuvettes at 25°C.

 

[Acetadehyde]

(mg/L)

[SO2]

mg/L

 

A1

 

A2

 

ΔAtotal SO2

 

% error

0

300

0.042

1.477

1.435

0.0

31

300

0.041

1.458

1.417

1.3

63

300

0.042

1.502

1.460

-1.7

125

300

0.042

1.498

1.456

-1.4

250

300

0.041

1.466

1.425

0.7

625

300

0.042

1.347

1.305

9.1

1250

300

0.045

0.279

0.234

83.7

 

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